1. Field of the Invention
Embodiments of the present invention generally relate to footwear, and more specifically to an actively ventilated shoe, in particular an athletic shoe.
2. Background Art
The technical development of shoes, in particular sports shoes, has advanced considerably in recent years. Modern shoe constructions are available that are adapted to compensate for the mechanical stress on a foot that arises when participating in various sporting activities. These shoe constructions provide a high degree of functionality and wearing comfort.
However, in spite of these important improvements, companies have been unsuccessful in manufacturing shoes that, in addition to providing necessary damping and support to the foot, also provide a comfortable climate for the foot. On the contrary, use of the foamed plastic materials common in modern sports shoes prevents heat and humidity from being sufficiently transported away from the foot to efficiently avoid excess heat buildup, unpleasant odor or the risk of diseases of the foot. This is particularly problematic in athletic shoes due to the increased body activity when participating in sports, which causes an increase in heat and humidity in the shoe.
For this reason different approaches have been proposed in order to achieve sufficient ventilation and fast removal of sweat.
U.S. Pat. No. 5,918,381 describes a shoe with a sole consisting of two layers. One layer contains a liquid which is moved during running and which powers a turbine. The turbine powers air-fans in the second layer of the sole that suck external air through lateral openings in the sole and pump it into the interior of the shoe.
U.S. Publication No. 2005/0060906 describes a shoe with three ventilators which pump air through lateral openings in the sole out of the shoe or into the shoe. Additionally, an air-conditioning unit pumps cool air into the shoe. The system is activated when a set temperature inside the shoe is exceeded.
In some cases, one disadvantage of these systems is that the air inlet and/or air outlet openings are arranged on the outside of the shoe. In such a configuration, there is a risk that moisture and dirt may enter the openings and thus the interior of the shoe. This can damage or even destroy the ventilation system.
In U.S. Pat. No. 6,041,518 fresh air is transported into the shoe via tubes that end at the upper edge of the laces of the shoe. However, even in this arrangement there is a danger that moisture and dirt may enter the tube. Thus, the use of covers is described to close the ends of the ventilation tubes. The diameter of the tubes is small and therefore the tubes provide a relatively small amount of ventilation.
In U.S. Pat. No. 3,273,264, an air-fan is built into the heel of a shoe. The air-fan sucks external air through an opening in the heel and pumps it into an opening in the interior midfoot area of the shoe. In some cases, one disadvantage of this approach is that the heel portion of a shoe generally experiences the highest impact forces during the gait cycle, and these forces can interfere with the operation of the ventilation system. In addition, because impact forces are at their peak in the heel, the heel portion of a shoe is generally provided with a significant amount of cushioning. Because the ventilation system described in U.S. Pat. No. 3,273,264 occupies a substantial volume of the heel, the system has the undesirable effect of reducing the amount of cushioning material that can be placed in the heel.
Further, U.S. Publication No. 2005/0235523 describes a shoe with a micro fan which is arranged on the outside of a shoe. In at least one embodiment, the fan pumps air into the shoe through small holes in the fabric of the shoe. A thermal switch controls operation of the fan. However, the fan can be easily damaged due to its positioning on the toe or exterior side of the shoe. There is also a danger that moisture and dirt will be sucked in by the fan. Furthermore, in this arrangement no fresh air is transported to the underside of the foot, which is where the most moisture collects and most heat is generated.
U.S. Pat. No. 6,865,825 relates to ergonomic systems with adapted surfaces and temperature control. The described systems of actuators and sensors are directed to medical therapy and do not provide solutions for a controlled ventilation of shoes.
German Utility model DE 200 16 825 U1 relates to a shoe-sock combination wherein the shoe comprises at least one climate zone which enables air exchange, and wherein the sock comprises at least one climate zone which enables air exchange. The arrangement of the climate zones of the shoe and the climate zones of the sock are harmonized with respect to each other.
The above-described approaches for ventilation suffer from several disadvantages, including lack of protection from moisture and dirt, insufficient air circulation inside the shoe, and insufficient cushioning in the heel area. Furthermore, the possibilities for controlling ventilation are limited, since a simple temperature control does not satisfy the complex and variable requirements for maintaining a comfortable climate in a shoe. Several of the shoes described above can be time-consuming to manufacture because the components of the ventilation systems are distributed in different locations of the shoe and therefore add steps to the manufacturing process. Alternately, the ventilation system is mounted on the outside of the shoe so that the system is not protected from the elements.
Thus, there is a need for an article of footwear, in particular a sports shoe, which overcomes at least some of the explained disadvantages of the prior art by, for example, providing effective ventilation to the interior of a shoe, satisfying the complex requirements of maintaining a comfortable foot climate, protecting the interior of the shoe and the ventilation system against moisture and dirt, and maintaining a streamlined manufacturing process.